Medulla Oblongata

Anatomy

• The lowest part of the brainstem; continues into the spinal cord at the foramen magnum.
• Ventrally the pyramids (corticospinal tract; 85–90% decussate) and the olive (inferior olivary nucleus — climbing fibers to the cerebellum).
• Dorsally the gracile and cuneate nuclei; nucleus tractus solitarius (NTS — visceral sensation, taste, baroreflex), dorsal motor nucleus of the vagus, nucleus ambiguus (IX, X), nucleus of XII.
• Area postrema (chemoreceptor trigger zone for vomiting); the pre-Bötzinger complex in the ventrolateral medulla (respiratory rhythm generator). Blood supply: vertebral artery, PICA, anterior spinal artery.

Functions

• Breathing rhythm; control of heart rate and blood pressure (baroreflex).
• Swallowing, coughing, sneezing, vomiting (area postrema).
• Vagal (parasympathetic) output and relay of visceral sensation to the brain (NTS → parabrachial → hypothalamus, amygdala, insula).
• Passage and decussation of sensory and motor pathways; tongue movements (XII), voice (X).

Connections and chemistry

• Vagus nerve (visceral afferent/efferent)
• NTS → hypothalamus, amygdala, insula
• Inferior olive → cerebellum
• Corticospinal tract (pyramidal decussation)
• Raphe obscurus/magnus → spinal cord (pain modulation)

Development

Developmental course through childhood and adolescence.

• Respiratory control matures after birth (apnea of prematurity).
• Medullary serotonergic abnormalities have been shown in sudden infant death syndrome (SIDS) (Kinney and Richerson, 2009).
• Vagal tone (RSA) develops in childhood in relation to emotion regulation skills.

Clinical

• Reduced HRV in anxiety disorders.
• Anorexia nervosa: bradycardia from vagal dominance.
• Nausea at SSRI initiation (area postrema 5-HT3); respiratory depression in opioid overdose (μ receptors in the pre-Bötzinger complex).
• Rett syndrome: breathing irregularities from brainstem autonomic dysfunction.
• Chiari malformation: headache, sleep apnea, difficulty swallowing.

Treatment

This region from the perspective of medication, psychotherapy and neuromodulation. Letter badges are evidence levels.

• Rett syndrome: trofinetide (a tripeptide analog derived from the N-terminus of IGF-1) is the first FDA-approved drug, from age 2 (March 2023). In 187 girls aged 5–20 it was superior to placebo on a behavior scale at 12 weeks; diarrhea (82%) and vomiting (29%) are common. Breathing irregularities need separate monitoring. A
• Nausea at SSRI initiation (area postrema 5-HT3) usually passes within 1–2 weeks; taking the drug with food and slow titration help. B
• In opioid overdose, rapid naloxone reverses the μ-receptor effect on the respiratory center (pre-Bötzinger); naloxone training is recommended for adolescents and their families. A
• Posterior fossa decompression in symptomatic Chiari malformation. B

Assessment

Neuropsychological tasks and measures that probe this region's function.

• Heart rate variability (HRV — an index of vagal tone)
• Respiratory sinus arrhythmia (RSA) — in emotion regulation research
• Swallowing assessment, orthostatic autonomic tests

Lesions and damage

Clinical findings expected with damage or dysfunction.

• Lateral medullary (Wallenberg) and medial medullary syndromes.
• Dysphagia, dysarthria; respiratory and cardiovascular failure are life-threatening.

In the model

How this structure is defined in the 3D model, and the data source.

Lower part of the CerebrA brainstem label (z < −47 mm). The template’s field of view cuts off the lower end of the medulla.

References

Full citations for the card; links go to the paper (DOI) or a PubMed search.

1. Beauchaine T. Vagal tone, development, and Gray's motivational theory: toward an integrated model of autonomic nervous system functioning in psychopathology. Dev Psychopathol 2001;13(2):183–214. DOI: 10.1017/s0954579401002012
2. Chalmers JA et al. Anxiety disorders are associated with reduced heart rate variability: a meta-analysis. Front Psychiatry 2014;5:80. DOI: 10.3389/fpsyt.2014.00080
3. Duncan JR et al. Brainstem serotonergic deficiency in sudden infant death syndrome. JAMA 2010;303(5):430–437. DOI: 10.1001/jama.2010.45
4. Kinney HC, Richerson GB et al. The brainstem and serotonin in the sudden infant death syndrome. Annu Rev Pathol 2009;4:517–550. DOI: 10.1146/annurev.pathol.4.110807.092322
5. Montandon G et al. PreBötzinger complex neurokinin-1 receptor-expressing neurons mediate opioid-induced respiratory depression. J Neurosci 2011;31(4):1292–1301. DOI: 10.1523/JNEUROSCI.4611-10.2011
6. Neul JL et al. Trofinetide for the treatment of Rett syndrome: a randomized phase 3 study. Nat Med 2023;29(6):1468–1475. DOI: 10.1038/s41591-023-02398-1
7. Smith JC et al. Pre-Bötzinger complex: a brainstem region that may generate respiratory rhythm in mammals. Science 1991;254(5032):726–729. DOI: 10.1126/science.1683005